tools [utils]: misc. improvements

- sort / restructure header usage
- use utils::toAsciiLower, same as asciiToUpper()

Change-Id: Ic5e7a369cea64cdb561471fb8c1246036263698d
Pick-to: 6.9 6.8
Reviewed-by: Alexey Edelev <alexey.edelev@qt.io>

src/tools/qtprotoccommon/utils.cpp

@@ -4,11 +4,8 @@
 
 #include "utils.h"
 
-#include <string_view>
-
-#include <cctype>
 #include <cassert>
-#include <regex>
+#include <cctype>
 #include <filesystem>
 
 namespace {
@@ -65,12 +62,7 @@ std::string replace(std::string_view where, std::string_view from, std::string_v
 
 void asciiToLower(std::string &str)
 {
-    const auto toLower = [](char c) {
-        if (!isAsciiAlpha(c))
-            return c;
-        return char(c | char(0x20));
-    };
-    std::transform(std::begin(str), std::end(str), std::begin(str), toLower);
+    std::transform(std::begin(str), std::end(str), std::begin(str), utils::toAsciiLower);
 }
 
 void asciiToUpper(std::string &str)

src/tools/qtprotoccommon/utils.h

@@ -6,6 +6,7 @@
 #define QTPROTOBUFGEN_UTILS_H
 
 #include <string>
+#include <string_view>
 #include <vector>
 #include <algorithm>
 #include <set>
@@ -68,7 +69,7 @@ std::string join(const T &container, std::string_view separator, std::string_vie
 
 size_t count(std::string_view s, char c);
 
-// ASCI check functions
+// ASCII check functions
 constexpr bool isAsciiUpper(char32_t c) noexcept
 {
     return c >= 'A' && c <= 'Z';